all about wiring diagram

Anyone who has designed circuits using the 555 timer chip will, at some time have wished that it may be programmed for longer timing periods. Timing lengths larger than a couple of minutes are tough to succeed in as a outcome of part leakage currents in massive timing capacitors change into vital. There is then again no reason to opt for a basically digital resolution just yet. The circuit shown here uses a 555 timer in the design but nonetheless achieves a timing interval of as much as an hour! The trick right here is to feed the timing capacitor now not with a constant voltage but with a pulsed dc voltage. The pulses are derived from the un smoothed low voltage output of the facility provide bridge rectifier.

The power provide output is just now not referenced to earth potential and the pulsing full wave rectified sign is fed to the bottom of T1 by the use of resistor R1. A 100-Hz sq. wave signal is produced on the collector of T1 as the transistor switches. The positive 1 of 2 of this waveform charges up the timing capacitor C1 by manner of D2 and P1. Diode D2 forestalls the cost on C1 from discharging through T1 when the sq. wave signal goes low. Push-button S1 is used to start the timing duration. This methodology of charging uses moderately low component worths for P1 (2.2 MΩ) and C1 (100 to 200 µF) however succeed ins timing periods of as much as an hour which is much longer than a regular 555 circuit configuration.